"We think the 'open' versus 'closed' argument is a smokescreen for what's really best for the customers," Jobs said. "We think Android is very, very fragmented and becomes more so every day. We think this is a huge strength of our approach when compared to Google's. We think integrated will trump fragmented every time."

Rubin didn't immediately respond to a request for comment. But if you're not up on your command-line interfaces, the tweet translates to making a directory, pulling in the Android source code, and building the operating system from scratch. In other words, exercising the full potential of open-source software, a pretty empowering idea for developers.

Open source, along with the closely related free software concept from which it stemmed, has rewritten many software industry rules. Open-source programs come with permission for anyone to see software's underlying source code, modify it, and distribute it themselves--all at no cost. But for most folks, that falls short of a real answer to Jobs' challenge.

There are indeed many people who have the abilities to make use of open-source software. But they are dwarfed by the number of people who don't or who simply can't be bothered to build their own binaries from scratch.

Since Sun Microsystems co-founder Scott McNealy has retired from public view, I'll step in with my own car metaphor relating to the powers granted by open-source software: few people want to change their car's oil themselves, much less rebore their engine's cylinders.

Of course, open-source software can have secondary appeal to ordinary consumers. If developers like it and can use it well, they can build things out of open-source software that regular folks will appreciate without having to know what led to it. Indeed, open-source software such as JQuery, memcached, Apache, MySQL, and Linux power all kinds of popular services on the Web.

This leads naturally to the audience that does care about Android's openness: the business partners central to Google's Android priorities. Those companies are enjoying the freedoms granted by Android, even if that means their needs sometimes overpower the best interests of Android phone customers who might want Android's native user interface and tethering options.

Google, meanwhile, keeps a pretty tight lock on future Android development. It's an open-source package, but the average outsider shouldn't have any illusions about being able to jump in and fiddle with the innards of a future version of Anrdoid such as Gingerbread or Honeycomb. You can bet that Samsung, Motorola, and HTC are getting a lot more openness from Google here than some hardware hacker who wants to build a phone OS from scratch.

Photo by screenshot by Stephen Shankland/CNET

Don't forget that Google often sidesteps openness. It updates its core search engine frequently without asking anyone's permission. It has built an online office suite and e-mail service whose interface and destiny the company controls. These are not open-source applications, but they're widely used, and with them, Google shows it can be very Apple-like in selecting what it thinks will work best for people and shielding them from the underlying complexity.

In rebutting Jobs, Google probably has a better case when it comes to the openness of software that runs on Android. Want Firefox or Opera Mobile browsers? Google Voice? You won't see those on iOS, at least today, but they're not a problem with Android. The Android Market may not have the richness of Apple's App Store, but it doesn't have many of its restrictions, either, and that's an area where the average customer is more likely to care about Android openness.

Apple has plenty to worry about when it comes to Android competition. It is a powerful operating system with a healthy applications market and strong partners. Fragmentation is a problem, but the multitude of Android designs--different screen sizes, keyboards, and prices--makes it adaptable. Competition is a real force within the Android ecosystem today.

But touting the ability to build Android from scratch is probably the easiest part of the Android threat for Apple to laugh off. As Apple has demonstrated, technology customers prefer finished products to raw materials.